


Washed Up

by equilateral_asshat



Category: Gravity Falls
Genre: F/M, pinecest - Freeform, pinescest - Freeform
Language: English
Status: Completed
Published: 2018-12-15
Updated: 2018-12-15
Packaged: 2019-09-18 11:39:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,304
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16994304
Author URL: https://archiveofourown.org/users/equilateral_asshat/pseuds/equilateral_asshat
Summary: This story was inspired by a furry porn comic that I literally can never remember the name of for the life of me (it also featured incest stuff!).





	Washed Up

A loud, horrific screeching startled Dipper awake. Sitting up, he swung his legs over the edge of the bedframe and knocked on the frame of the top bunk. **  
**

“Mabes, Mabes get up, the clock is screaming at us,” he groaned, grabbing his phone to check the time. His heart dropped; it was half past seven in the morning. He had set the alarm for seven on the dot, he had sworn it. “Aw hell, Mabel, get-”

He was cut off as his sister’s foot swung over the edge of her bedframe, landing squarely on top of his head as she yawned and stretched. Using his noggin as a stepping stone, she playfully hopped out of her own bed and landed on the floor with a lazy stumble.

“I’m not a rung on a ladder, Mabel, we’ve been over this,” he complained, rubbing his neck as he stood up. The only response that got for the moment was a tired, throaty chuckle. “I’m serious, I’ll just sleep on the couch if you’re going to keep stomping on me when we get up.”

“Relax, broseph,” she mused as she wobbled her way over to her dresser. Dipper frowned as she stumbled along, taking her sweet time; moving into a tiny, shared apartment for college had originally felt like a fantastic idea. They would have less rent to pay for alone, and the fact that they had gotten into the same school felt like a godsend, to boot. But now, seeing how his sister behaved in the mornings since they had gotten free from high school, he was having doubts.

Firstly, the apartment was the very definition of tiny, feeling more like a live-in hotel room than an actual living space. The main area was one major room, with the living area and kitchenette split between a room that was barely fifteen feet by twenty feet. Directly off of this space was the only bedroom, which had been too cramped for two twin beds to exist in same same floor space, so they had to get bunk beds to compensate. Right next to the bedroom, was the bathroom, which was thankfully roomy enough for the two of them to maneuver around each other at the sink.

Secondly, his sister’s carefree attitude about schedules and adhering to set timelines was starting to grate on his nerves. She had probably reset the alarm for a later time than he had, which had now thrown the morning into disarray off the bat. They barely had time to both get cleaned and dressed without missing the bus to campus. He glowered at the back of her head as he pictured her, giggling while she punched buttons on the alarm clock in order to sleep in. As he stared daggers there, she bent down to dig in the bottom drawer of her dresser, and the third problem sprung to mind.

Over the course of the last few months, despite all of his annoyances with his sister’s laziness in the mornings, certain feelings had managed to rise to the surface. Things that had nagged at him back in his early throes of puberty were coming back, with them crammed into this tiny space together. He was starting to develop not-so-brotherly feelings for his own sister.

Her manner of dress while they were alone in the apartment was part of the issue, he had decided; she had a tendency to come through the door, wiggle her arms into her shirt, and then they would wiggle back out, bra in one hand. The thin fabric of her shirts did little to hide the shape of her breasts underneath, and even though she was his sister, Dipper had caught himself staring on more than one occasion. To make matters worse, her idea of pajamas was more or less a short t-shirt and a pair of panties. As he found himself staring, at the delicate, supple curve of her buttocks, he noted that she had opted for the frilly pink ones again. They were his favorite pair, and he hated that he had a favorite pair of his sister’s underwear. It wasn’t his fault she would bend over at the dresser and shake her rump to music she had going in her head.

Once he realized he had been staring, he then noticed another problem had cropped up. Hands shooting to his lap, he stood up and grabbed his predetermined clothing for the day off of a chair at the foot of his bed. “Dibs on the shower,” he muttered as he escaped the bedroom.

 _Dipper, you CANNOT keep staring at your sister when she does that. One of these days she’s gonna notice before you do, and then she’ll notice THIS problem, and probably disown you,_ he groused internally, staring down at the tent in his pajama pants. He frowned as he stripped down, turned the shower on full blast, and stepped into the tub. Drawing the curtain closed, he tried to mentally will the erection he was sporting away. It merely bobbed at him, as if taunting him for his urges.

“Nope, not gonna do that again. Especially when she’s not in the next room,” he told it. It twitched enticingly. “I am not going to rub one out to the thought of Mabel’s ass, dammit.” It only gave another small throb, and he groaned. “Fine if it’s the only way to make you go away, just this once,” he said, wrapping his fingers around the girth and starting to stroke.

Visions of Mabel’s skimpy outfits, her wiggling backside, and her nipples straining against her shirt fabric seemed to flutter about behind his eyelids, the scenery there sometimes giving way to deeper fantasies where she would kiss his neck, or rub a hand over his thigh. He shuddered, both in bliss and self resentment; nobody should be this worked up over their sibling.

“Hey, waterhog, you alive in there?” He screamed a somewhat undignified scream, flailing and tugging the shower curtain open enough to tuck his head out into the open room, where his sister was preparing to brush her teeth.

“Mabel, dammit, I’m in the shower! Get out!” he demanded, and she just waved him off.

“We’ll miss the bus if I waste time waitin’ around on you to finish scrubbing up, bro-bro,” she said matter-of-factly as she glopped toothpaste onto the bristles of her bedazzled toothbrush. He narrowed his eyes at her, and she merely fluttered her eyelashes at him innocently.

“I’m gonna reset the alarm clock tonight and I do _**not**_ want you to set it forward again,” he stated, yanking the curtain back closed. She merely hummed as the sound of bristles scrubbing pearly whites came from her direction. It was good enough of an answer for him to just take it, for now. “I’m serious, if we’re late today because of your shenanigans, you have to buy the next three pizzas for pizza night.”

“Dipper, we’re in college! Ya gotta let go of all these stingy inhibitions you have about being late to class and all that. Attendance isn’t graded, and one of your classmates will probably be able to give you their notes on any lectures you happen to miss,” she noted. He grumbled, refusing to admit she was right. His classmates had, so far, been fairly helpful in keeping him caught up whenever he had missed class for any reason. But still, he refused to let himself turn into the stereotypical college slacker.

“Yeah, sorry sis,” he relented. “I just hate the idea of getting into a rut of slacking off and letting myself get bad about sticking to my plans and all that, you know? I don’t wanna repeat of junior year.” Mabel snorted from the sink.

“Yeah yeah, you got so lazy in physics you got a D minus and panicked, and it took you what, one week of catch-up work to get it up to a B before the exam?”

“I barely got an A!” he retorted.

“Yeah, but you still got it,” she fired back with gusto.

“Okay, fine, I concede. Now can we just hurry up and get ready for the day?”

“Sure,” she quipped. Suddenly the shower curtain was yanked open, and one of her feet was in the tub, between him and the water.

“M-MABEL! What are you doing, out, OUT!”

“Dipper, what is your beef?” She stepped all the way in and turned her back to him, nude as the day they were born. He took great care to make sure he stared straight at the back of her head.

“My ‘beef’ is that you’re naked and in the shower while _I’M_ naked and in the shower!”

“We used to take baths together all the time!”

“We were five years old when that stopped, Mabel. Please, why are you doing this?!”

“Hey, you wanted me to hurry up. If we share the shower, we’ll save time,” she explained. He drug his hands over his face with a moan; arguing with her was pointless.

“Okay, fine, but no more of this. It’s bad enough you scamper around here half dressed.”

“Pffff, I haven’t got anything you haven’t seen, if your internet history is to be believed,” she joked, handing him a bottle of her body wash. “Get my back soaped up?”

He took the bottle and stared at it, then her shoulders and slope of her back. This was bad, very bad. Touching her naked, wet flesh would probably cause certain things that had gone away, during their argument, to spring right back up.

“Hey, ya gonna do it or not? The longer you dilly-dally, the more time we lose!” she chimed. With a sigh he popped open the cap and squirted some of the pink, fruity smelling goop into his hand, then handed the bottle back to her waiting hand. He rubbed his hands together to evenly distribute the soapy slime and started to work it into her shoulders. She shivered at the initial chill of the soap, then relaxed into his grip with a breathy sigh.

He had not been ready for that. He felt something twitch below the belt and he tried to mentally will it away as he ran his hands in slow circles down her shoulder blades, then the middle of her back, and finally over her hips. His mind wandered as his hands dipped lower, lower…

“So, uh, hey there, Dip-dop?”

“Hmm?”

“You seem to be havin’ an awful lotta fun soaping up my butt, you gettin’ weird back there?”

A blink of his eyes and a good stern look at his hands informed him that he had, indeed, been lathering soap bubbles up on Mabel’s rear for the last minute or so. His mind started to go into primal instinct, fight-or-flight kicking in as he struggled with what to say. As he wrestled internally with these thoughts, she gave a wiggle.

“Okay, weirdo, you gonna let go or-OOP!” she began, but without warning his arms circled around her waist and tugged her back against his abdomen.

“Do you have _any_ idea of what you acting like this does to me?!” he hissed in her ear, half angry, half begging for reason. “You prance about half naked, you wiggle your ass at me while you dig for clothes, and now you have me soaping you up naked in the shower?! Do you know how weird and twisted I feel?! Do you have any idea what kind of unbrotherly things go through my mind when you do this stuff?!”

SIlence hung in the air for a beat, neither of them speaking.

“Well, uh,” she began again, “I guess I can say I have a good eight, eight-and-a-half inch idea of what goes through your noggin?” she offered. He made a small sound of confusion, and she gave her hips a roll backwards, which made him suddenly very aware of the fact that he had his manhood lodged in the cleft of her backside. He froze, like a deer in headlights, certain she was about to scream rape and murder.

“I… uh… I’m sorry, it-”

“You gonna use that?”

His brain flatlined. The squeak of confusion this time must have been perfectly translated into ‘whatever do you mean, sister dearest, I have no idea what you are implying,’ because she gave another roll of her hips and a small whine of eager intent bubbled up in her throat.

“Cuz if you you’re not gonna, I will,” she whispered. The only sound that seemed be coming from anywhere was the hammering of his heart in his chest. She was giving him the okay? She was actually _offering_ to do something they could never undo, never come back from?!

A lone hand snaked between their wet bodies, feminine fingers gently pushing his hips back away from her, and then giving a curious rub to the stiff spire of flesh he was sporting. He sucked a breath in through his nose, trying to fight a whimper as he felt fingers wrap around him, angling him down as her hips pressed back again.

As instinct grabbed him this time, it made his hips press forward, eager and willing. The first thrust pushed him below the mark, the warmth of her womanhood gliding over the top of his length. Both of them gasped as his hips rolled, both reveling in the sensation.

“If… if we do this, we can’t undo it. We can’t take it back,” he mumbled in her ear, voice shaky.

“I know,” she sighed breathlessly, hips gyrating to roll his flesh against her own.

“I want to, I want to so bad, but I don’t want to hurt you. I love you, and-”

“I love you too, but are you gonna wax poetic, or are you gonna fuck me,” she interrupted, her hand snaking fingers into the hair on the back of his head, tugging him into a quick, fiery kiss. “You think you’re the only one with weird, taboo fantasies? You think I’m innocent when I push my nip-nops against my shirt for you to see?” She growled as she nipped at his chin, hips rolling again.

They stayed like that for a second or two, each one daring the other to make that next, final leap into uncrossable territory. Finally, a throaty growl gurgled up in Mabel’s throat as she gave the grip on Dipper’s hair a squeeze.

“One time offer, take it or leave it. Going once, going twice…” she teased, and his hips tugged back, gave a slight dip as he adjusted, and he pushed once. Both twins gasped together as flesh encircled flesh, that line now crossed. He gave an experimental roll against her backside, and she cooed lovingly. “F-fuggin’ sold…”

Dipper gave another push against Mabel’s backside, then pulled back before thrusting forward again. The moan that escaped his sister as she bent at the waist, releasing his hair so she could brace herself against the wall drove him to do it again, and then again. Soon the shower was awash with the sound of skin slapping into skin, wet and powerful as each meeting of bodies was announced.

“G-good god, you feel amazing,” he blurted, his fingers digging into her hipbones as he tugged her against his lap. She rolled her hips, head tossing back as she pressed against him with an almost hungry shove of her backside.

“Speak for yourself, Dip, fffffuuck,” she said, her tone encouraging. Her words spurred him onwards, each thrust delivered with more eagerness to please than the last. His hands wandered up her sides, then shifted to cup her breasts. Each one was a perfect handful, and the playful squeeze he gave made her legs quiver. The next grope allowed a squeak to escape as she trembled. He had found a weak spot, it seemed, and he would do well to remember it.

He used the grip for extra leverage, hips meeting rump with more gusto than before, each twin making noises of bliss as they neared the peak of pleasure. Dipper nuzzled up to her ear, stating that he was close. She just nodded, her sudsy rear slapping into him as she pressed back into each shove he gave.

“C-can, can I… inside…?” he stuttered, a few words not making it in the transition from brain to mouth. She nodded, slamming back against him even harder.

“Gods yes, please, I need to feel it,” she moaned. That sound was the last thing he needed, giving that little nudge that would send him spiraling over the plateau of orgasm.

His lap found her ass one last time as he tugged her close and held fast, buried inside of her sex, his member began to pulse, each throb delivering another shot of spunk against her inner walls. Her back arched, and her breath hitched in her throat as she came along with him, thighs clamping together as her velvet embrace went from a soft grip to a vice, determined to milk him for every drop he was worth.

They stood under the water, each panting until the inevitable softening of his manhood and her own tightness pushed them apart, the results of their union slowly dribbling onto the floor of the tub, and swirling towards the drain. Neither of them spoke, simply basking in the afterglow. A minute or two passed, and without a word, Dipper stepped out onto the bathmat, grabbing his towel and starting to dry himself off as his mind raced.

He and Mabel had just done a very, very wrong thing. And sure, she had pretty much made the move from “awkward brother dryhumps” to “incestual intercourse”, but he felt guilt starting to crash down immediately. Had he been pressuring her? Did she feel like she _had_ to do it, after he had confessed about those horrible, sinful feelings he was having for her? How could she forgive him for any of this?!

While his conscience waged war in his mind, he failed to notice that she had pulled back the shower curtain until she planted a quick kiss on his temple.

“I love you, Dipper,” she said against his forehead. “Now stop lettin’ your brain do that thing where you spaz out over stuff and go get dressed, or else we’re gonna end up missing the bus.” He turned to face her, and saw the honest, sincere smile she wore. There was not one hint of regret in her eyes. He just smiled back for a moment, and then a look of dread fell over his face.

“Oh no, _the bus!_ ”

=========

Standing on the corner, Dipper and Mabel watched the eight-o-clock bus pull away from the stop, right on schedule, while they were a block away, each panting with effort as it sped off towards the school campus. Dipper groaned and buried his face in his hands.

“Dammit, I knew it. I knew this would happen, as soon as I woke up.”

“Aw, cheer up, Dippingsauce,” Mabel said, patting him on the shoulder. He snapped his head around, half glaring, half confused. A hint of a smile was on her lips, and her eyes glittered with mischievous intent.

“Cheer up? What good can come of me missing class on the week of a test?” he retorted. She smirked.

“I was thinking we could, oh, skip today, and go lounge around the apartment?” His face twisted with confusion, but watched as her arms disappeared into her shirt as she jogged backwards down the sidewalk. They reappeared, bra in one hand. “If I keep going at this rate, I’ll be naked by the time we get back!”

He shot to his feet and tore off after her, half to keep her dressed in public, and half to get her undressed when they got home.

**Author's Note:**

> This story was inspired by a furry porn comic that I literally can never remember the name of for the life of me (it also featured incest stuff!).


End file.
